New Google Maps Requirement: How to Get Your Google Maps API Key
In June 2016, Google announced that it was shaking up the way users add Google Maps to their website. Going forward, new users will need a Google Maps API key.
That means, for the time being at least, existing Google Maps users are unaffected – the maps currently being displayed on your website will continue to function. How long it will continue to work is anyone’s guess. My advice is to be prepared for changes, and grab yourself a Google Maps API key now.
If you’re looking to add a new map to your website, the choice is taken out of your hands – you need that API Key or no maps.
Source: New Google Maps Requirement: How to Get Your Google Maps API Key